Condensing metallic vapors



Jan- 27, 1931. G. T. MAHLER ET AL L792 CONDENS ING METALLIC- VAPORSFiled May 5' 1925 2 Sheets-Sheet l Jan. 27, 1931.

G. T. MAHLER ET AL CONDENSING METALLIC VAPORS 2 Sheets-Sheet '2 FiledMay 5, 1925 INV NTO S Gl. me, JJM

ATTORNEYS ratus for Patented Jan. 27, 1931l UNITED STATES PATENTl'OFFICE GEORGE T. MAKLER, ERWIN C. HANDWERK, .AND EARL H. BUNCE, OFPALMRTON,

PENNSYLVANIA, ASSIGNORS TO THE N. Y., A CORPORATION OF NEW JERSEY NEWJERSEY ZINC COMPANY, OF NEW YORK,

. CONDENSING METALLIC VAPORS ,v Application filed May 5,

This inventiourelates to the condensation of metallic vapor, and Amoreparticularly zinc vapor, and has for its object the provision of animproved method of and appacondensing metallic vapor and especially zincvapor. y

Metallic zinc or spelter, when producedby the reduction of oxidized zincores at high temperatures, is almost universally made at the presenttimein zinc distillation or spclter furnaces having a number of relativelysmall retorts to the outer ends of which condeusers are attached. Theretorts are usually mounted at a slight inclination, usually inclineddownward from'the butt or closed end towards the open or outer end. Thecondenser is in effect an extension or elongation of the retort,although usually mo nted in a substantially horizontal position, andhence not in exact alignment with the elongated axis of the retort. Thezinc vapor and other gases pass in a substantially horizontal line fromthe retort through the condenser, and the exhaust gases escape throughthe open end of the condenser. The eiliciency of this present customarycondensing apparatus is far from satisfactory, only about 6() to 65% ofthev the remainder metallic zinc vapor passing out of theretort beingcondensed as metallic zinc or spelter, being condensed as "blue powderor burning at the mouth of the condenser to zinc oxide andlost.

l/Ve vhave discovered that the eliiciency of u condensation of zincvapor can be very substantially improved by appropriately circulatingthe vapor over a lm of molten zinc. of suitable area and held at acarefully controlled temperature. The necessary filmv of molten zinc ispreferably provided and maintained upon the ceiling and the upright Wall`Aor walls of the condensing chamber, and thezinc vapor entering thechamber 1s caused to repeatedly circulate and Contact r with the ilm ofmolten zinc. The desired` circulation of the zinc vapor isadvantageously brought about by passing a stream or current of zlncvapor mto the condensing chamber and causing this stream of vaporftoimpingefagainst al ceiling so disposed as to 1925. .Serial N'o. 28,056.

uniformly defiect-the zinc vapor against the film of molten right wallor chamber.

In our preferred practice, the condensing chamber' is disposed so thatthe stream of zinc vapor passes upwardly through the bottom thereof andimpinging against the ceilmg is uniformly deflected outwardly and.downwardly over the film of molten zinc on= the ceiling and the upright(preferably ver-v tical) Wall or walls of the condensing chamber. Thezinc vapor is thus'caused vto re'- peatedly circulateover and in Contactwith the 'film of molten zinc, of appropriate area, and at the propertemperature, and condenses thereon. .The condensed zinc serves tomaintain on the ceiling and on the upright wall or Walls of thecondensing chamber the desired^film of mol-ten zinc, and the excess zincdrops off or Hows down these walls toan appropriate well at the bottomof the condensing chamber and is there collected.

We have found that in addition to the area of the condensing surfacecareful controlof the temperature of the ceiling and upright wall orWalls of the condensing chamber is necessary forthe optimum efficiencyof condensation of the zincvapor. When the temperatureof the ceiling andupright wall (or walls) is properly controlled substantially allvof thezinc vapor is conzinc on the ceiling and'up-l walls of the condensingdensed as metallic zinc or liquid spelter, and

less than 10% and frequently as little as 1 to 2% of the total zincentering the chamber condenses as fblue powder or uncoalesced zincdroplets, the balance of the, zinc being con ensed as metallic zinc orliquid spelter.

In the accompanying drawings, we have illustrated what we now considerthe best modes of practicing the invention. In these drawings, we haveshown our improved condenserfin conjunction with a verticalretort orshaft furnace, but We desire to have it'understood that the invention isnot limited to this particular type of zinc distillation furnace but, onthe contrary, the invention is of general applicability and can beadvantageously used for 'condensing zinc or other me 100 tallic vaporwithout regard to the source of the vapor.

In the accompanying drawings Fig. 1 is a front sectional elevation of avertical retort or shaft furnace for reducing oxidized zinc oresprovided with Athe im- Figs. 1, 2` and 3 of the drawingscomprises avertical retort 10 of tire-clay or other appropriate material. Theretort 10 is surrounded, for the greater part of its length, by alaboratory or heatingchamber 11. The heating chamber 11 is built Withina furnace structure comprising an outer steel shell or casing 12,

van intermediate layer 13 of heat-insulating material, such asSil-o-cel, and a lining made up of lire-brick 14 covered with graphiteblocks or plates 15. Appropriate openings 16 are provided through theWall of the furnace structure for permitting the insertion of pyrometersWithin the laboratory or heating chamber 11, for ascertaining andcontrolling the temperature throughout the length of this chamber.

The furnace structure is mounted on an appropriate foundation 17. 'Ihebottom of the retort 10 opens into a closed chamber or pit 18 having aclean-.out door 19.

Any appropriate means may, of course, be employed for heating theretort. 10. Thus. for example, ire gases may be conducted through thelaboratory 11 and around the retort 10. In the apparatus illustrated inFigs.'1, 2 and 3, the heating of the retort is effected by electricenergy. The electric heating or resistance element comprises` twographite rods 20 extending through the top of the furnace structure andresting on graphite blocks 21 slightly below the center of the chamber11. The lower portion of the rods 2() are hollow and have a spiral slotsov as to provide a helical resistance path for the flow of the electriccurrent. One terminal of the source of electric energy is connected toone of the graphite rods 20 and the other terminal of the source ofelectric energy is connected to the other graphite rod 20. the electriccircuit between the lower ends of the two rods 2O being completedthrough the graphite blocks 21 and the graphite lining l5. Either director alternating current may be used for supplying electric energy to thegraphite rods 20. 1

The bottom 'of the chamber 11 is provided with two graphite resistancerods or elements tically disposed wall 25. A flat circular ceil' ing 26covers the top of the cylinder 25, and an annular plate 27 partiallycloses the bottom of the cylinder. The cylinder 25 and plates 26 and 27are made of heat refractory `Inaterial, such as fire clay, carborundum,

mixtures of the same, or the like. These three elements may beintegrally united or separately formed and joined together to constitutethe novel and improved plug-hat condenser of ourI invention.

A nozzle 28 is attached to the bottom plate 27. The diameter of thecentral opening in the plate 27 and the internal diameter of the nozzle28 are less -than the diameter of the retort 1() and these threeelements are axial# ly in alignment. The nozzle 28 extends upwardly toabout midway of the condensing chamber provided within the cylinder 25.

The ceiling 26 -has a `central opening 30 loosely covered by a plate 31.The exterior of the condenser (cylinder 25 and ceiling 26) is coveredwith an appropriate layer 29' of heat insulating material. In practice,we have found dust coal admirably adapted as the heat insulatingVcovering for the con.- denser. From the loosely packed insulatingmaterial (coal) around the plate 31, the carbon monoxide gas escapesfrom the opening 3() of -the condensing chamber and burns in the air.

The annular space between the nozzle 28 and the cylinder 25provides awell for collecting molten zinc, and molten zinc is tapped from thiswell, from time to time, through a taphole 32.

The mixture of zinc vapor and carbon monoxide gas (resulting from thereduction of the oxidized zinc ore in the retort 10) passes out of thetop of the retort into the nozzle 28. A11-upwardly flowing stream orcurrent of zinc vapor thus passes through the bottom of the condenserand4 into the condensing chamber. This stream of zinc vapor impingesagainst the fans out over the ceiling 26, and is uniformly deflecteddown the side of the upright wall 25, as indicate-d by the arrows inFig. l of the drawings.

drafted across this constantly renewed fresh film 'of molten zinc andcondense thereon.

, Thus, the tihn of molten zinc provides a nucleus upon whichcondensation of the zinc vapor readily takes place. The exhaust gases,Ior`tne most part carbon monoxide, escape through the opening 30,passing underneath the loose plate 31 and through tallic zinc or liquidspelter.

.The metallic zinc condensing on the Wall of the cylinder flows downthis wall `into the molten metal well at the bottom of the condensingchamber. The molten zinc accumulates in this well and is periodicallyremoved therefrom through the tap-hole 32.

The film of molten zinc on the condensing walls -need not be continuous,and in practice may consist of minute drops or globules of molten zincwhich substantially cover the innersurface of the wall or Walls. By afilm of molten zinc, we mean a thin layer of molten zinc, notnecessarily continuous, but sutliciently extensive in area tosubstantially cover the inner or condensing surface of the cylinder 25and ceiling 26.

It is important that the temperature ofthe walls of the condensingchamber (25 and 26) be` carefully controlled. If the temperature ofthese walls is too high, the gases escaping through the opening willcarry too much zinc vapor, and if the temperature of these Walls is toolow an excessive amount of blue powder will be formed. l/Ve have found atemperature of from 500 to 850o C. satisfactory,'and when the condensingWalls are maintained Within this temperaturey range,

' very eicient condensation of the zinc vapor to metallic zinc or liquidspelter results.

Ve prefer to regulate and control the tem perature of the condensingwall or walls by regulating the amount of external heat insulation onthese walls. In practice, we periodically insert a pyrometer(thermo-couple) into the condensing chamber (preferably .through the topopening 30) and when the temperature within the chamber is too high,

we decrease the amount of external heat insulation, and when thetemperature is too low,

We increase the amount of this external heat insulation. This externalheat insulation may advantageously consist of a layer of dust coal, orother appropriate heat insulating material, loosely packed around theoutside of the condenser. The amount of external heat insulation aboutthe condenser is then varied by varying the thickness of this layer ofheat insulating material. Y.

The size and proportions of the condenser s are varied in accordancewith the amount of zinc vapor to be condensed. Vorking with a retort(10) 8 inches in internal diametei-.and

10 feet long, charged with zinc silicate ore (containing approximately45-50% zinc) .andy dust coal in about equal amounts, and

Working off the charge in 8 hours, we have secured excellent resultswith a condenser built of a mixture' of carborundum and ireclay,approximately 12 inches in internal diameter and 11 inches high(internal), the walls of the condenser being 1 inch in thickness. Thenozzle 28 was approximately 3 inches in internal diameter and extendedabout 4 inches Within the condensing chainopening.30 and into the top ofthe retort through the nozzle 28. Too large a nozzle,

however, is not desirable, since a. certain amount ot the condensed zincdrops oit the ceiling 26, and it the diameter' otl the nozzle- 28 is toolarge, an objectionable amount of molten zinc dro-ps back into theretort and has to be redisti'lled.

The condenser of Fig. 5 is relatively higher and narrower than thecondensers of Figs. 1 and' 4. Care must be taken not to unduly lengthenthe condenser, since under such circumstances the topof the condensingchamber' becomes relatively cool and an excessive amount o f blue powdermay be formed. In the condenser of Fig. 5 vthe same reference charactershave been used ,to designate The nozzle 28 of the condenser lcorresponding or equivalent parts as in Fi g.' 1.

lVhile we prefer to arrange thc entrance nozzle or orifice of thecondenser so that it is coaxial with the condensing chamber, such anarrangei'neut is not necessary. In Fig. G

the nozzle 28 for conveying the zinc vapor y to the condensingchamber isdisposed at'one side of the chamber.

The condenser of Fig. 7 is provided with spaced Walls. The exhaust gasesfrom the condensing chamber vpass through the space between the' twowalls and thus promote the heat insulation of the condensing chamber.Corresponding Ior equivalent parts of the condenser ot' Fig. 7 areindicated by the saine reference characters asin Fig. l. The 'condenserproper (25-26) is surrounded by a spaced shell 33, of fire-clay or thelike.4 The gases' escape `from the condensing chamber through openingsor ports 35 in the cylinder 25. The gases then How through the spacebetween t-he shell 33 and the condenser (25-26) and escape to theatmosphere positioned openings trated a multiple condenser adapted to becondensed.

used with a vertical retort or shaft furnace of relatively largediameter.A As illustrated in Fig. 9. this condenser consists of three ormore units, and vembodies theA general structural features of thecondensers of Figs; 1 and 7. l

. The condensers herein illustrated and described are generally ofcircular section.`

However, it is to be understood that this configuration is not anessential part of the invention, but is adopted in practice principallybecause of its practical convenience. The improved condenser of ourinvention maybe square, rectangular, oval and indeed of any desired,sectional configuration.

The improved condenser of our invention is principally characterized byits upright and preferably vertical condensing Wall (or walls) andsubstantially horizontal ceiling. The condensing surface or area of theupright Wall (or walls) and ceiling are carefully proportioned withrespect to the amount of zine vapor to be condensed'in a unit of timeand this condensing surface is held at a carefully controlledtemperature. The current or stream of entering zinc vapor is con# ductedinto the condensing chamber through an opening, preferably constricted,in the bottom of t-he condenser. and rising upwardly in'lpinges againstthe ceiling and is deflected over the condensing surface. The zinc vaporrepeatedly circulates over the condensing surface` covered with a filmof molten zinc, until The exhaust gas is preferably "permitted toVescape through the looselv covered opening in the top of the condenser.

However, if desired, the upright4 Wall of the condenser may be providedwith suitable openings or ports for the escape of the exhaust gas. i

The zinc vapor enters the condensing chamber at an approximately rightangle to the surface of the molten zinc in the collecting Well. Themolten zinc in this-Well preferably surrounds the conduit through whichthe zinc vapor passes on its wayinto the condensing chamber. Thetemperature of the Vmolten zinc in the collecting Well is controlled toprevent boiling oft-he Vmolten' zinc. This may be convenientlyaccomplished by appropriate control of the amount of external Aheatinsulation about this portion of the condenser.

The upright wall or Walls of the condenser are preferably cquidisjtantfrom theentering de nsation.

yissue from the top of the vertical' retort 10,

the two factors that play a great part in the efficiency of condensationare the temperature and pressure Within the condensing chamber. Both of-these factors are controlled by the size and the proportions of thecondenser. If the temperature of the condensing Walls is too great, zincvapor will escape and be lost. If the temperature is too low, the zincwill condense in the form of blue powder. rather than molten metal. Ifthe pressure in the condensing chamber becomes too great, it Will have adeadening effect on the velocity of the reaction Within the verticalretort, and will, therefore, ad-

' verselyaffect the recoveries. Ifthe pressure in the condensingchamberbecomes too low,

the zinc will condense as blue powder,

amount of zinc vapor may be held fairly con-v stant and uniform, and acondenser of appropriate size and proportions may he provided for thisuniform set of conditions.

ico

lu the case of' hatch or intermittent chargmixed gases passing from themuflle or re-.

tort is than in the second four hours of the operation. ,During thefirst four hours ofthe operation, the condenser, therefore, should havea relatively large radiating surface and relatively large volume inorder to keep the temperature and pressure down to Within the limits forefficient condensation.

During the latter four hours of the operation. theratio of zinc in thegases increases and the quantity decreases so that it is necessaryr toprovide more external heat insula- Vtion for the condenser in order tomaintain a high` enough temperature for efficient con- It is impossibleto change the volume of the' condensing chamber and, therefore, duringthis latter stage of the operation the pressure in the condensingchamfrom said last mentioned opening into thc ber is too low forefiiciet condensation, and condenser.

some of the zinc may, therefore, be con- In testimony whereof We atixour signadensed as blue poWder.- tures.

In constructing a condenser for batch or GEORGE T. MAHL'ER. 70intermittent operation, 'it is preferable tol ERWIN C. HANDWERK.compromise between the two extreme condi- EARL H. BUN CE.

. ing therein, a plate loosely covering saidv tions, rather than toprovide a condenser of appropriate size and proportions for one or theother extreme conditions.

Weclaim v 1. A condenser for metallic vaporscomprising a substantiallyupright enclosing wall, a ceiling for said wall havingan openingtherein, a plate loosely covering said opening, and a closure at thebottom of said wall having an opening for the passage of metallic vaporinto the condenser.

2; A condenser for metallic vapors comprising` a substantially uprightenclosing Wall, a ceiling for said Wall having an opening therein, aplate loosely covering said opening, an external covering ofheat-insulating material for said Wall and ceiling, and a closure at thebottom ofA saidwall having an opening for the passage of metallic vaporinto the condenser.

3. A condenserfor metallic vapors comprising a substantially uprightenclosing wall, a ceiling for said wall, an external covering oflooselypacked granular heat-insulating material for said wall and ceiling, and

. a closure lat the bottom of said wall having an opening for thepassage of metallic vapor into the condenser.

4. A- condenser for metallic vapors comprising a substantially uprightenclosing Wall, a ceiling for said wall having an openopening, anexternal covering of loosely packed granular heat-insulating materialfor said Wall and ceiling, and a closure at the bottom of said Wallhavingan opening for the passage of metallic vapor into theconenser. 1

5. A 'condenser for metallic-vapors comprising a -vertically disposedcylindrical en@ closing wall, a ceiling for said Wall having aff openingtherein, a plate loosely covering said opening, an externalvcovering ofheat insulating material for said Wall and ceiling, a closure at thebottom of said wall having an opening therein, and a nozzle extendingup- Wardly from said opening into the con-v denser.

6. A condenser for. metallic vapors comprising a vertically disposedcylindrical enclosing Wall, a ceiling' for said Wall having an openingtherein, a plate loosely covering said opening, an external covering ofloosely packed granular heat-insulating-material for said wall andceiling, a closure at the bottom of said Wall havingian opening thereinand a constricted nozzle extending upwardly los

